Wheelchair anti-tip apparatus

ABSTRACT

An anti-tip apparatus for a wheelchair includes a main tube extending laterally and rearwardly from the rear frame upright of a wheelchair, and an extension tube slidably received in each main tube and spring-biased to a retracted position. The extended ends of the extension tubes are joined by a transverse support tube to provide rigidity and strength to the apparatus. A wheel or coaster at the end of each extension tube allows the chair to roll rather than capsize over the tube ends, and reduces the shock to the chair. A manually releasable spring detent latch on each main tube holds the apparatus in the extended position, allowing the wheelchair occupant safely to tip the chair back onto the extended wheels to negotiate steps and curbs, and to retract the apparatus when manuvering in close quarters. The transverse support tube is manually collapsible, permitting the wheelchair to be folded for storage or transportation.

[ Nov. 19, 1974 United States Patent Breacain WHEELCHAIR ANTI-TIPAPPARATUS [57] ABSTRACT An anti-tip apparatus for a wheelchair includesa main [76] Inventor: Stephen J. Breacain, 3260 Delaware St., Oakland,Calif. 94602 Aug. 8, 1973 Appl. No.: 386,736

[22] Filed tube extending laterally and rearwardly from the rear frameupright of a wheelchair, and an extension tube slidably received in eachmain tube and spring-biased to a retracted position. The extended endsof the extension tubes are joined by a transverse support tube {2?}llffiiiiiiiiiiiiiiiiii:1:11:11if??? fiflflfi iii pioiiiie iigiiiiiy andiiieiigiii ii iii ippiiiiii A [58] Field of Search 280/52 5 wheel orcoaster at the end of each extension tube al- 280/21 1 282 293; lows thechair to roll rather than capsize over the tube ends, and reduces theshock to the chair. A manual] Y releasable spring detent latch on eachmain tube holds the apparatus in the extended position, allowing thewheelchair occupant safely to tip the chair back onto the extendedwheels to negotiate steps and curbs, and to retract the apparatus whenmanuvering in close quarters. The transverse support tube is manuallycollapsible, permitting the wheelchair to be folded for storage ortransportation.

Assistant Examiner-Michael Mar Attorney, Agent, or FirmHarris Zimmerman15 Claims, 10 ng g r PATENTEL NOV 1 9 m4 sum 2 or '4 SHEET 30F 4PATENTE' BUY 1 91974 PATENIELHUVIQIHH 3,848,883

SHEU MW 4 FIGJ WHEELCHAIR ANTI-TIP APPARATUS BACKGROUND OF THE INVENTIONA conventional wheelchair known in the prior art typically includes tworear wheels of large diameter and two forward wheels of small diametersecured to a frame, with the seat and back rest disposed on the frame sothat the greater part of the weight of the occupant is resting on therear wheels. This standard wheelchair configuration provides bothlateral and forward stability, but does not allow the wheelchair to betilted rearwardly without the risk of tipping over completely.Unfortunately, this rearward tilting motion must be frequently employedby the occupant if he/she is to negotiate curbs, steps, hills, etc.,without the aid of an attendant. In the prior art many devices have beendisclosed to stabilize a wheelchair in the rearward direction, includingrearwardly extending structures supporting wheels which prevent morethan a minimum of rearward tilting. These structures, however, havetended to make the wheelchair far too unwieldly in close quartersmaneuvering such as in elevators, hallways, crowds, etc. Furthermore,these structures, due to their rigidity, have not been adaptable tomodern, folding wheelchairs now in common use.

SUMMARY OF THE INVENTION The present invention is directed toward anextendable anti-tip apparatus for a wheelchair which allows thewheelchair to be tilted rearward by the occupant without the danger oftipping over, and is retractable, when not in use, for maneuvering inclose quarters. Furthermore, the anti-tip apparatus may be folded inconcert with a folding wheelchair, permitting the chair to be easilystored and transported. The apparatus con sists of a main tube securedto each of the rear frame uprights of the wheelchair by close toleranceclamping brackets, and extending horizontally and rearwardly of thewheelchair. An extension tube received within the main tube is slidablymounted on an axially disposed rod. Joining the extended ends of theextension tubes is a horizontal, transverse slide tube assembly, whichcomprises two transverse tubes hinged to a medial member, and a slidetube slidably disposed upon the medial member and portions of thetransverse tubes. The slide tube immobilizes the hinges, and permits theassembly to add rigidity and strength to the extension tubes. Slidingthe slide tube entirely onto one of the transverse tubes allows thehinges to operate, so that the assembly may fold in concert with afolding wheelchair. A wheel or caster is secured to each extension tubeat the junction of the slide tube assembly, permitting the wheelchair,when resting on the wheels, to roll forwardly or backward, andpreventing rearward tipping of the chair.

THE DRAWINGS FIG. 1 is a side view of the present invention in use;

FIG. 2 is a side view of a portion of the present invention;

FIG. 3 is a side cutaway view of a portion of the present invention inthe extended position;

FIG. 4 is a side cutaway view of the portion of the present inventiondepicted in FIG. 3, shown in the retracted position;

FIG. 5 is a plan view of the present invention;

FIG. 6 is a detailed sectional view taken along line 6-6 of FIG. 5;

FIG. 7 is a rear view of the slide tube assembly of the presentinvention;

FIG. 8 is a rear view of the slide tube assembly in the DESCRIPTION OFTHE PREFERRED EMBODIMENT As shown in FIG. 1, the occupant ll of awheelchair 12 must resort to tilting the wheelchair rearwardly tonegotiate unassisted a step or curb 13 or any similar obstacle. In doingso, the occupant risks tipping over, inviting serious injury, or, at theleast, an arduous struggle to right the wheelchair and regain its seat.The common wheelchair with the main wheels 14 secured to the rearupright 16 of the frame to support most of the weight of the occupant,and the swivelling front wheels 17 secured in sockets 18 to provideforward stability to the chair, has no means for providing rearwardstability in the situation depicted. However, the anti-tip apparatus 19of the present invention, secured to the rear frame upright 16 andextending rearwardly of the frame, does provide such stability.

Each side of the anti-tip apparatus includes a main tube 21 which iswelded at one end to a clevis-type bracket 22 which secures the maintube to the upright 16 by virtue of the close fit of the main tube inthe clevis, and engagement of the outward tine with a section of tube 15welded to the upright 16, and with the axle'carrier 65. An extensiontube 23 received in the main tube terminates in a wheel or caster 24 ofhard black rubber or the like which bears on the ground when thewheelchair is tilted rearwardly. A springdetent latch 26 secured to themain tube locks the extension tube in the fully extended position, (asshown in FIG. 2), or the retracted position. A clamp 27 secured aboutthe rear upright 16 and bolted to the bracket 22 prevents removal of theanti-tip apparatus from the wheelchair.

Between the tines of the clevis bracket 22 a compressed resilient plug28 received in the end of tube 21 is disposed to cushion any shocktransmitted from the anti-tip apparatus to the wheelchair frame, totension the clevis bracket against the rear upright 16 and to preventinjury from the end of the tube in case of accident. The interiorportion of the pad is formed into an annular recess 29 which receivesone threaded end of a rod 31. The rod extends through an annular openingin a resilient block 32, and slidably receives the extension tube 23through the opening 33 in the end thereof. The rod passes through anannular opening in block 34 and is secured thereto by screw 40, andterminates in a rubber washer 36. Adjacent the ends of block 32 is ametal washer 30 and a nut 35, the outer diameters of the block and thewashers equalling the inner diameter of the tube 21. Tightening the nuts35 causes the washers 30 to compress the block, increasing the blockdiameter to compress the block against the tube interior and maintainbolt 31 and extension tube 23 securely in place. The block 34 and thewasher 36 are equal in diameter to the inside diameter of tube 23.

The present invention comprises a left main tube and a right main tube,each secured to a rear frame upright 16. A transverse slide tubeassembly 40 of variable length extends between the respective extensiontubes to strengthen and add rigidity to the structure in the extended orretracted position, as shown in FIG. 5.

Welded to each main tube is the spring detent latch 26, which looks theextension tube in the fully retracted or fully extended position. Asshown in FIG. 6, the latch comprises a housing 41 which slidablyreceives shaft 42 through suitable openings. The shaft 42 includes ashoulder portion 43 which retains one end of a compression spring 44,the other end of the spring bearing on the inside end of the housing. Tothe shouldered end of the shaft is secured a generally cylindricalrubber handle 46 which is parallel to the main tube 21. An arm 47extends from the other end of the shaft 42 and is transverse thereto andto the handle 46. A detent 48 extends from the arm and protrudes into anaperture 49 in the main tube, engaging one of the two apertures 51 inthe extension tube which registers with the detent when the extension isdisposed in either the fully extended or fully retracted position.Compression spring 44 urges the shaft and the arm 47 into engagementwith an aperture 51 by continually applying force to the shoulder 43.Manual force on the handle 46 to counter the spring force removes thedetent from aperture 51, as shown in phantom in FIG. 6, permitting theextension tube to translate between the fully extended and retractedpositions.

The slide tube assembly 40 includes sockets 53 welded to the left andright extension tubes and transverse thereto, each socket fixedlyreceiving one end of a support tube 54. The other end of each supporttube terminates in a hinge member 56, as shown in FIG. 7, which istrcadedly received in tube 54. Each hinge member is secured to medialmember 57 by hinge pins 58 which are parallel to the main tubes 21. Aslide tube 61 disposed about the medial member and portions of thesupport tube 54 is maintained in such a disposition by protrusions 59and 60 on the support tubes. In such a disposition the hinge members 56are nearly immobilized, so that the slide tube assembly is maintainedrigid and provides support for the extension tubes and rigidity for theanti-tip apparatus. The length of the slide tube assembly may beadjusted to fit any width chair by screwing the members 56 into or outof the tubes 54.

The slide tube assembly is designed to be collapsed to accommodate thefolding of the wheelchair. Protrusion 60 is a spring-loaded button whichis manually depressable, allowing the tube 61 to be translated axiallyto a position over the support tube to free the hinge members 56 forrotation. Folding of the wheelchair frame causes the main tubes 21 tomove towards each other, with the support arms 54 rotating upward on thehinge pins 58, and the extension tubes rotating within the main tubescorrespondingly. The slide tube assembly acquires the collapsedconfiguration depicted in FIG. 8 and FIG. 9, the slide tube beingmaintained in its non-engaged position by the socket 53, and the angularrelationship of the medial member 57 with the hinge member 56. Thepresent invention in use on a folded wheelchair is depicted in FIG. 10.It should be noted that the entire anti-tip apparatus may bechromeplated or otherwise finished to match the finish of thewheelchair.

Thus it may be seen that the present invention may be employed with afolding wheelchair without impairing the collapsibility of the chair.Furthermore, the anti-tip apparatus, although collapsible, is anextremely lightweight, rigid structure which can support a large portionof the weight of the wheelchair and its occupant. And, due to the novelextension tube construction, the anti-tip apparatus may be extended foruse and retracted for convenience, providing a long-sought combinationof safety and comfort for the disabled.

I claim:

1. In combination with a wheelchair having main rear wheels, an anti-tipapparatus comprising:

horizontal member means secured to the frame of said wheelchair adjacentthe axes of rotation of said wheels and extending laterally andrearwardly of said wheels of said wheelchair in normally parallelrelation to a ground surface; and

extension member means slidably secured to said horizontal member meansand extensible to a position rearwardly of said wheels for preventingexcessive rearward tipping of said wheelchair.

2. The anti-tip apparatus of claim 1, wherein said horizontal membermeans includes a main tube secured to a rear frame member of saidwheelchair.

3. The anti-tip apparatus of claim 2, wherein said extension membermeans includes an extension tube slidably received within said maintube.

4. The anti-tip apparatus of claim 3, further including a rod secured tosaid main tube and disposed axially therein, said rod being slidablyreceived in an opening in one end of said extension tube.

5. The anti-tip apparatus of claim 3, further including latch means forlocking said extension tube in one or more positions within the maintube.

6. The anti-tip apparatus of claim 5, said latch means including adetent extending into an opening in the wall of said main tube andregistering with and engaging one of a plurality of apertures in thewall of said extension tube.

7. The anti-tip apparatus of claim 6, further including resilient meansfor biasing said detent into engagement with one of said plurality ofapertures, and manual means for disengaging said detent from said one ofsaid plurality of apertures.

8. The anti-tip apparatus of claim 1, further including bracket meansfor securing said horizontal member means to a frame member of saidwheelchair adjacent and above the axes of said wheels.

9. The anti-tip apparatus of claim 1, said bracket means comprising aclevis bracket secured to said horizontal member means, said clevisbracket including two parallel and spaced apart tines for receiving saidframe member securely therebetween.

10. The anti-tip apparatus of claim 3, said wheelchair including a leftrear frame member and a right rear frame member, and parallel left andright main tubes secured respectively to each of said rear framemembers, each main tube receiving an extension tube therein.

11. The anti-tip apparatus of claim 10, further including a collapsiblesupport assembly transverse to and joining said extension tubes.

12. The anti-tip apparatus of claim 11, wherein said support assemblyincludes left and right support members and a medial member, eachsupport member hinged at one end to said medial member, the other ingretaining means for retaining said slide tube in a non-interferingdisposition with said hinges of said medial member.

15. The anti-tip apparatus of claim 11, wherein said collapsible supporttube assembly is manually adjustable in length to accommodatewheelchairs of differing widths.

1. In combination with a wheelchair having main rear wheels, an anti-tip apparatus comprising: horizontal member means secured to the frame of sAid wheelchair adjacent the axes of rotation of said wheels and extending laterally and rearwardly of said wheels of said wheelchair in normally parallel relation to a ground surface; and extension member means slidably secured to said horizontal member means and extensible to a position rearwardly of said wheels for preventing excessive rearward tipping of said wheelchair.
 2. The anti-tip apparatus of claim 1, wherein said horizontal member means includes a main tube secured to a rear frame member of said wheelchair.
 3. The anti-tip apparatus of claim 2, wherein said extension member means includes an extension tube slidably received within said main tube.
 4. The anti-tip apparatus of claim 3, further including a rod secured to said main tube and disposed axially therein, said rod being slidably received in an opening in one end of said extension tube.
 5. The anti-tip apparatus of claim 3, further including latch means for locking said extension tube in one or more positions within the main tube.
 6. The anti-tip apparatus of claim 5, said latch means including a detent extending into an opening in the wall of said main tube and registering with and engaging one of a plurality of apertures in the wall of said extension tube.
 7. The anti-tip apparatus of claim 6, further including resilient means for biasing said detent into engagement with one of said plurality of apertures, and manual means for disengaging said detent from said one of said plurality of apertures.
 8. The anti-tip apparatus of claim 1, further including bracket means for securing said horizontal member means to a frame member of said wheelchair adjacent and above the axes of said wheels.
 9. The anti-tip apparatus of claim 1, said bracket means comprising a clevis bracket secured to said horizontal member means, said clevis bracket including two parallel and spaced apart tines for receiving said frame member securely therebetween.
 10. The anti-tip apparatus of claim 3, said wheelchair including a left rear frame member and a right rear frame member, and parallel left and right main tubes secured respectively to each of said rear frame members, each main tube receiving an extension tube therein.
 11. The anti-tip apparatus of claim 10, further including a collapsible support assembly transverse to and joining said extension tubes.
 12. The anti-tip apparatus of claim 11, wherein said support assembly includes left and right support members and a medial member, each support member hinged at one end to said medial member, the other ends of said support members secured to the respective left and right extension tubes.
 13. The anti-tip apparatus of claim 12, further including a slide tube slidably received about said support assembly, said slide tube immobilizing said hinges of said medial member when disposed about said medial member.
 14. The anti-tip apparatus of claim 13, further including retaining means for retaining said slide tube in a non-interfering disposition with said hinges of said medial member.
 15. The anti-tip apparatus of claim 11, wherein said collapsible support tube assembly is manually adjustable in length to accommodate wheelchairs of differing widths. 